Valve seat insert ring



July 10, 1956 R. N. HONEYMAN ET AL 2,753,858

VALVE SEAT INSERT RING Filed May 27, 1952 h P 5 2'12: .2 7 5 Eoaser JYHavEwm/v I'own e0 6". Pate 3636 M M, 9 W by H/Zys.

VALVE SEAT INSERT RING Robert N. Honeyman, Lyndhurst, and Edward G.Pekarek, Willoughby, Ohio, assignors to Thompson Products, Inc,Cleveland, Ohio, a corporation of Ohio Application May 27, 1952, SerialNo. 290,222

3 Claims. (Cl. 123-188) The present invention relates to a powderedmetal valve seat insert for internal combustion engines, the inserthaving a body portion with desired expansion characteristics and aseating face portion with desired wear and corrosion resistantproperties. The invention is also directed to a method of preparing sucha powdered metal valve seat insert by means of which an intimate bondingis achieved between the powdered metal making up the facing portion andthe powdered metal comprising the body portion of the valve seat insert.

In the process of the present invention, the body or base of thepowdered metal insert is provided by placing finely divided ironparticles, or other ferrous compositions containing predominatingamounts of iron in a suitable die, and then positioning thereoverpowdered refractory metal particles having good oxidation resistance andhot strength properties. The composite powdered metal charge is thenmolded under suitable pressure conditions to provide a self-sustaininggreen compact. The green compact is then sintered to secure a goodbonding of the ferrous material with the facing material, coined, andinfiltrated with a metal having good heat conducting properties. Theinfiltrant metal forms a network within the pores of both the facing andthe ferrous body portions and improves the bond between the powderedmetals of these portions.

in order to further improve the physical characteristics of theinfiltrated ferrous base material, the infiltrated valve seat insert isthen solution heat treated and precipitation hardened. In this way, thebody or base of the insert can be formed of a metal or mixture of metalswhich have thermal expansion characteristics similar to those of themetal of the particular engine into which the ring is to be seated. In apreferred embodiment of the present invention, small amounts ofaluminum, up to 5% by weight, are included in the ferrous compact makingup the body portion of the valve seat insert, as we have found that theaddition of the metallic aluminum to the ferrous base reduces shrinkageof the iron base material so that it will match the shrinkage of thefacing material during sintering. The expansion characteristics of thebody or base portion can thus be controlled to compensate for anydifference in shrinkage of the materials of the body and of the facingportions that might otherwise occur during sintering. The addition ofaluminum has the further advantage that aluminum acts as a deoxidizer inthe iron and reduces any oxidized particles in the region of theinterface between the dissimilar powdered metals to produce a uniformlygood bond.

The facing portion of the valve seat insert is formulated from highlyrefractory materials, alloys, or mixtures of metals capable ofeffectively resisting the severely corrosive conditions occasioned bythe presence of lead compounds in the combustion zones that result fromthe burning of fuel containing tetraethyl lead. The refractory metal maycontain high proportions of chromium and need not be weldable, since themechanical pressing, sinter "nited States Patent' ice ing, and theinfiltrant network develop the required bond with the body metal.

Heretofore, valve facing materials were selected with a view to theirWelding characteristics so that they could be effectively puddled ontothe base metal. The available base metals were likewise limited to thosemetals which were compatible with the puddled-on facing material andwhich could be suitably fabricated. The present inven tion now makespossible the selection of metals for the base which are best suited fora particular engine block or head and metals for the facing which arebest suited for resisting wear and corrosion. Both the base and thefacing are porous and are united by a metal'of good thermalconductivity. The facing is capable of dissipating substantially moreheat than would be the case if the facing surface were deposited on thebody in the form of a puddled-on deposit.

In a preferred form of the invention, the body metal consists of finelydivided iron particles obtained by reducing mill scale and containingcarbon in amounts from 0.01 to 1.7% by Weight. The addition of smallamounts of aluminum, up to 5% by weight of the mixture, is also highlydesirable in order to reduce shrinkage of the iron base material. Theferrous powder has an average particle size of from minus to about 325mesh. Ungraded fines, finer than 325 mesh, may be present in amounts upto 20%.

The material for the facing may be selected from a large variety ofmetals and alloys which possess oxidation resistance characteristics,but is not necessarily limited to those metals or alloys which have goodwelding characteristics. Typical among the alloys which can be used forthe process of the present invention is the alloy identifiedcommercially as AMS-5373A containing from 63% to 68% cobalt, 27% to 30%chromium, and 2% to 6% tungsten. Other suitable alloys include nickelbase alloys, particularly those alloys containing from 15% to 25%chromium, 50% to 80% nickel, balance iron with about 0.1% carbon. Amechanical mixture containing 50% powdered iron and 50% powderedchromium by weight is also suitable. An alloy having exceptionaloxidation corrosion resistance, and suitable for the purposes of thepresent invention, is one containing 50% to 65% by weight nickel, 20% to35% by weight chromium, 6% to 9.5% tungsten or molybdenum, or mixturesof the two; 1.0% to 2.5% carbon, 0.05% to 0.5% silicon, 0.01% to 0.10%zirconium, and the balance iron.

In a preferred form of the invention, the refractory alloy powder isprepared by an atomizing process in which a molten aloy is atomized withwater jets, thereby producing finely divided, generally rounded, as wellas spherical particles. This powder has about the same particle size asthe iron powder but the particles are more nearly spherical in shape.When compacting particles of this type, the rounded shapes provide onlylimited areas of contact with the adjoining particles, so that the refractory metal particles upon compacting are quite porous, having adensity only of about 60% of theoretical before coining, and about 80%after coining. The shaped particles are desirable in facilitatinginfiltration because they provide a network of cavities between theparticles which are easily filled by the infiltrant metal. If desired,the metal for the facing can be mixed in a ball mill with about 5% byweight of the infiltrant metal, such as copper. The infiltrant metalthereby coats the particles and this coating further facilitatesinfiltration. In addition to the atomizing process, other processes forobtaining prealloyed powder can be employed for the purposes of thisinvention. Instead of using a prealloyed powder, a premixture of theproper composition of ingredients within the ranges given above may beused. An object of the present invention is to provide an improvedmethod for manufacturing valve seat inserts for internal combustionengines by means of which two dissimilar powders are united togetherinto a single well bonded compact, and the compact is then infiltratedwith a lower melting metal having good heat conducting properties.

Another object of the present invention is to provide a method formechanically bonding together two powder compositions of differentchemical composition into an integral self-sustaining shape prior tosintering of the compact and infiltration of the compact with a molteninfiltrant metal.

Another object of the present invention is to provide an improved valveseat insert for internal combustion engines containing a body portionconsisting essentially of a ferrous compact clad with a facing materialintegrally united therewith, the facing material consisting of acompacted mass of refractory metal or refractory alloy particles.

Another object of the present invention is to provide an improved valveseat insert for an internal combustion engine in which the ferrous bodyportion of the composite valve seat insert contains added amounts ofaluminum to reduce shrinkage of the iron base material, and further forimproving the bonding characteristics of the two dissimilar powderedmetal compositions making up the composite valve seat insert.

Other objects and features of the invention will be apparent to thoseskilled in the art from the following description of the annexed sheetof drawings, which, by way of preferred examples only, illustrates themethod and articles of the present invention.

On the drawings:

Figure l is a cross-sectional view, with parts in elevation,illustrating the manner in which the ferrous particles making up thebody of the valve seat insert are introduced into the compacting dieassembly;

Figure 2 is a view similar to Figure l and illustrates the position ofthe lower punch element of the die assembly after it has been lowered toallow the ferrous material to settle and leave a predetermined void atthe top of the die cavity;

Figure 3 is a view similar to Figures 1 and 2 and illustrates the twopowder compositions within the compacting die cavity, and alsoillustrates the'position of the upper punch member which cooperates withthe lower punch member to compact the powder compositions into anintegral structure;

Figure 4 is a cross-sectional view of the completed valve seat insert;

Figure 5 is a plan view of the insert; and

Figure 6 is a cross-sectional view, with parts in elevation, of amodified form of the valve seat insert produced according to the presentinvention.

As shown on the drawings:

The compacting assembly illustrated in Figures 1 and 3, inclusive,comprises a compacting die 10 having a cylindrical cavity, cylindricalcore rod 11 disposed therein and an annular lower punch member 12slidably receivable within the annular space between the wall of the diecavity and the core rod 11 and closely fitting relationship therewith. Asupply of finely divided iron particles 13, which may contain addedamounts of carbon and aluminum as previously explained is distributed inthe cavity of the die 10 over the upper surface of the lower punchmember 12. The excess iron powder is struck off from the surface of thedie 10, so that the surface of theiron particles 13 is substantiallyflush with the upper surface of the die 10. A molding lubricant such aszinc stearate, in amounts of about 1% by weight is mixed into the ironpowder to facilitate compression.

After the ferrous particles have been distributed in the cavity, thelower punch member 12 is lowered as indicated in Figure 2 to leave thevoid 15 in the die cavity above the ferrous particles 13, as shown inFigure 2.

Refractory metal particles, identified by numeral 16 in Figure 3 aredistributed into the void 15 above the ferrous particles 13.

An annular upper punch member 13 having an axial bore 17 of sufficientdiameter to engage the outer periphery of the core rod 11 is thenlowered into the die cavity to compress the ferrous particles 13 as wellas the refractory particles 16 into a single, self-sustaining compact.Depending upon the ultimate density to be achieved in the compact,compacting pressures of from 30 to 80 tons per square inch may beemployed. 7 In most instances, sufficient pressure will be employed toproduce a compact in which the ferrous particles have about 70% of thetheoretical density of iron, while the refractory particles, because oftheir spherical shape, have a density of only about 60% of theoreticaldensity. In general, the porosity of the ferrous compact will be in therange from 15% to 40%, with 30% being preferred.

After molding, the green compact is sintered at tem peratures from about1900" F. to about 2500 F. in a non-oxidizing atmosphere such ashydrogen. After sintering, the compact is cold coined to desireddimensions at pressure of about 30 to 80 tons per square inch, and atthis stage, the ferrous body ring has a density of about 75% to 90% oftheoretical.

The cold pressing of the two powder compositions together in the moldingcavity, as well as the addition of aluminum, produces a good mechanicalbond between the dissimilar metal compositions making up the bimetallicvalve seat insert. The heat and corrosion resistant facing material issecurely bonded to the ferrous base by an intermingling of powderparticles during die filling and pressing, as well as by the sinteringoperation.

The sintered composite metal insert is then infiltrated .with a lowmelting metal having good heat conductivity,

- such as manganese, nickel, chromium, silicon, and

titanium in amounts from about 0.1% to about 2% may be added. Whilecopper and copper alloys are the preferred infiltrant materials, otheralloys such as nickel alloys, cobalt alloys, chromium alloys, and othergood heat conducting metals such as silver and silver alloys can also beemployed as infiltrants.

The single compact may be infiltrated by providing a ring of copper orcopper alloy, and disposing it above a preformed compact. This assemblyis then introduced into an infiltrating furnace maintained attemperatures above the melting point of the infiltrant. When a copperalloy is the infiltrant material, temperatures of about 2000 F. to 2300F. are used.

Since the forrous body ring will ordinarily have a porosity of about30%, while the refractory metal facing will have a slightly higherporosity, and since the infiltrant metal substantially fills the poresof the rings, the resulting infiltrated compact will contain at leastabout 30% copper. The proportion of copper, however, can be varied overa wide range, and may extend from about 5% to about 35%. In order toimprove the strength and wear properties of the infiltrated compact, theassembly is solution heat treated to diffuse the cuprous metal into theferrous matrix of the ferrous ring. In addition, the refractory metal oralloy and the ferrous matrices of the composite ring are diffused intothe cuprous infiltrant phase{ The solution heat treatment is carried outat temperatures within the range from about 1000 F., to 2000 F., andpreferably at 1600 F. for a relatively short period of time such asone-half hour. After solution heat treatment, the infiltrated insert isoil quenched and reheated to effect precipitation hardening. The heattreatment precipitates both iron and some refractory metal alloyconstituents from the copper phase, and copper from the iron andrefractory alloy phase. Temperatures for precipitation hardening are inthe range from about 900 F. to 1200 F., the periods of time of treatmentdepending upon the temperatures employed. At a temperature of 925 F., asuflicient amount of precipitation hardening can be effected by atreatment time of one hour, followed by air cooling.

The finished valve seat insert is illustrated in Figures 4 and 5, andincludes a ferrous matrix 20 and a refractory metal matrix 21 joinedtogether at this interface 22 by means of mechanical bonding as well asby interdiffusion of the materials during sintering and an infiltrantnetwork which extends through the pores of the compacts and is alloyedwith the metals of both matrices.

An alternative embodiment of the present invention is illustrated inFigure 6 of the drawings. In this form of the invention, ferrous metalparticles are distributed in the molding die and then shaped with astrike-off tool prior to filling of the die cavity with the refractorymetal particles to provide a generally arcuate surface 24. Subsequently,refractory metal particles are introduced into the mold cavity over thearcuate surface 24, and the surface of the refractory metal particles ismade flush with the top of the die. By compacting, sintering andinfiltration of the two powder compositions, the ferrous metal 25 andthe refractory metal 26 are joined together along the contoured partingline 24. This structure reduces the amount of refractory metalcomposition used as well as providing for better intermingling of theferrous particles and the refractory metal particles during compressionof the powdered compositions.

From the foregoing description, it will be understood that thisinvention provides a powdered metal composite valve seat insert with afacing composed of a metal or alloy which is best suited for valvefacing purposes, and a body ring composed of a metal which is bestsuited for its compatability with the engine body or block in which itis to be mounted. The two powdered metal compositions are united in theform of an integral compact and further united through the medium of acommon infiltrant metal network which has good heat transfer properties,so that the facing is in good heat transfer relation with the enginebody.

It will be understood that various modifications and variations may beeffected without departing from the scope of the novel concepts of thepresent invention.

We claim as our invention:

1. A valve seat insert for an internal combustion engine comprising anannular body portion including a powdered iron compact, a facingconsisting of a powdered refractory metal compact, said facing havingsubstantially the same inner and outer diameter as said annular bodyportion, said facing being in face to face contact with said annularbody portion with the interface between said facing and said bodyportion containing intermingled particles of refractory metal and iron,and a network of an infiltrant metal extending into said facing and saidiron compact strengthening the bond holding the same together into anintegral structure.

2. A valve seat insert for an internal combustion engine comprising anannular body portion including a powdered iron compact, containingcarbon in amounts up to 1.7% by weight and aluminum up to 5% by weight,a facing consisting of a powdered refractory metal, said facing havingsubstantially the same inner and outer diameters as said annular bodyportion, said facing being in face to face contact with said annularbody portion with the interface between said facing and said bodyportion containing intermingled particles of refractory metal and iron,and a cuprous network extending through said facing and said ironcompact.

3. A valve seat insert for an internal combustion engine comprising anannular powdered iron compact having an axial bore and a flared uppersurface, an annular facing consisting of a refractory powdered metalcompact having a complementarily flared surface in face to face contactwith said flared surface of said powdered iron compact, the interfacebetween said facing and said body portion containing intermingledparticles of refractory metal and iron, and a cuprous network extendingthrough said facing and said iron ring.

References Cited in the file of this patent UNITED STATES PATENTS1,959,068 Stoll May 15, 1934 2,004,259 Weiger June 11, 1935 2,035,165Jardine Mar. 24, 1936 2,048,222 Rehmann July 21, 1936 2,100,620 Wirreret al Nov. 30, 1937 2,136,690 Jardine Nov. 15, 1938 2,154,288 ScholzApr. 11, 1939 2,401,483 Hensel et al. June 4, 1946 2,456,779 GoetzelDec. 21, 1948 2,549,939 Shaw et al. Apr. 24, 1951 FOREIGN PATENTS432,974 Great Britain Aug. 7, 1935 565,520 Great Britain Nov. 14, 1944OTHER REFERENCES Materials and Methods, April 1946, Cemented Steels, byPeters; pp. 987-988.

